Author Topic: HP proprietary IC replacement  (Read 488 times)

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Offline JKKDev

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  • Country: si
HP proprietary IC replacement
« on: December 21, 2018, 12:00:59 pm »
Hey :)

I'm looking for any pointers to figure out if I could replace this IC with another.
 
The topology can be seen here. EDIT: the whole board schematic for reference.

From the service manual about the theory of operation:
Output amplifier A5U2 is a shunt-feedback differential amplifier whose transimpedance converts the current gain of A5U1 (the other proprietary IC on this board) to a voltage gain at the input of the CRT. The CRT's vertical section is the distributed line type with a 330-ohm terminating impedance.

What I'm seeing on the board:
-delay line coming in to the A5 board has stabile voltage (A5U1 input)
-voltage prior to the A5U2 (A5U1 output) is stabile at exactly 28V as stated in manual
-voltage after the A5U2 is unstable between 30V and 50V (should be 40V) - nothing connected to the input of the scope

My question:
-Is it reasonable to assume the input current is stable as the voltage doesn't change?
-Can I replace this IC with something currently available?

Thank you and have a nice day/night :)
« Last Edit: December 21, 2018, 12:15:26 pm by JKKDev »
 

Offline jfphp

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Re: HP proprietary IC replacement
« Reply #1 on: December 21, 2018, 01:26:07 pm »
HP Part number ? Scope ? Is it a maintenance problem for a lot of scopes or do you need just one to repair your scope ?
 

Offline JKKDev

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  • Country: si
Re: HP proprietary IC replacement
« Reply #2 on: December 21, 2018, 02:06:52 pm »
HP Part number ? Scope ? Is it a maintenance problem for a lot of scopes or do you need just one to repair your scope ?

HP part numbers:

A5U1 - 5081 3022
A5U2 - 5081 3024 (the one in question)

From what I know they are on the vertical output amplifier boards of HP 1715A and 1725A. They might be in others but I haven't looked too closely.

I've seen at least a few other threads with a problem with this IC.

EDIT: Never mind I just found a solution   :phew:
 


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